[lwip-users] ping w/o LWIP_TIMERS

[chrysn]

hello lwip users,

i found another problem in the ping example, this time with master lwip
and master -contrib branch: when running NO_SYS=1 && NO_SYS_NO_TIMERS=1,
the ping example does not build any more. it does include components
that would rely on sys_timeout, but when there are no timeouts, it's
usable nevertheless.

attached patch ifdefs the appropriate sections out if not LWIP_TIMERS.

moreover, in order to successfully receive a response, something in the
ip version handling has to be adjusted. pbuf_header is called in
ping_recv with -PBUF_IP_HLEN -- but on dual-stack systems, this is -40
bytes. as a result, the iecho struct points 20 byte deep into the ping
data. i worked around it by explicitly stating pbuf_header(p, -20) and
pbuf_header(20) when restoring -- i don't know which constant should
rather be used there (something like PBUF_IP4_HLEN?).

best regards
chrysn

-- 
To use raw power is to make yourself infinitely vulnerable to greater powers.
  -- Bene Gesserit axiom

ping-wo-lwiptimers.patch
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